Electric Train Drive Control for Regenerative Braking Stability
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Solution Overview
Problem
During regenerative braking in electric trains, insufficient regenerative load can lead to sudden loss of braking power, causing abrupt deceleration changes and reduced riding comfort due to the transition from regenerative to mechanical braking.
Innovation Solution
A drive control device with a power controller that reduces regenerative braking force through an alternating current rotating machine using a predetermined reduction pattern with a ramp reduction time longer than 0, allowing the mechanical brake to increase power and minimize deceleration changes when the regenerative load is insufficient.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If regenerative braking is used to obtain braking power, then energy recovery is improved, but when regenerative load is insufficient, overhead line voltage rises causing equipment damage risk
Solution Approach 1:
The patent introduces a third rail as an intermediary load to consume excess regenerative power when overhead line voltage rises. The third rail acts as a buffer that absorbs the regenerative energy that would otherwise cause dangerous voltage buildup, enabling continuous regenerative braking operation without interrupting energy recovery processes.
Solution Approach 2:
The system dynamically switches the regenerative power discharge path based on voltage conditions. When overhead line voltage exceeds the predetermined threshold, the control unit redirects power flow to the third rail, changing the operational parameter of where regenerative energy is consumed. This allows the system to adapt to varying load conditions and maintain safe voltage levels.
2Object-affected harmful factors
If inverter circuit operation is stopped to protect from overvoltage, then equipment protection is improved, but regenerative braking force is lost instantaneously causing abrupt deceleration changes
Solution Approach 1:
The third rail serves as a mediator that maintains braking force continuity. By providing an alternative path for regenerative power dissipation, it prevents the abrupt stop of inverter circuit operation that would otherwise occur to protect equipment, thereby maintaining stable braking force through the intermediate third rail load.
Solution Approach 2:
The control unit detects voltage conditions in advance and proactively redirects regenerative power to the third rail before overvoltage damage can occur. This preliminary action prevents the need for sudden inverter shutdown, maintaining braking force stability by anticipating and preventing the harmful condition rather than reacting to it.
3Force
If mechanical brake supplements regenerative braking, then total braking force is maintained, but mechanical brake response time causes deceleration changes
Solution Approach 1:
The patent converts the potential harm of insufficient regenerative load into a benefit by utilizing the third rail as an artificial load. This allows regenerative braking to continue operating effectively even when natural regenerative load is insufficient, eliminating the need for mechanical brake supplementation and avoiding the associated response time delays.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach stabilizes braking force and improves riding comfort by gradually reducing regenerative braking power and allowing mechanical braking to compensate, preventing abrupt deceleration drops and extended braking distances.
Implementation Method 1
a so-called regenerative brake is used that obtains braking power by regenerative operation of the alternating current rotating machine
Implementation Method 2
the switching device (SW) of the overvoltage control unit assumes a continuous conducting condition (ON) and the electric charge in the filter capacitor is discharged
Data Source
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AI summary
Objective: To reduce fluctuations in deceleration of an electric train and improve riding comfort even when the regenerative load is lacking during a regenerative brake operation. Resolution means: A drive control device (1) for an electric train according to this invention comprises a switch (4) for connecting or opening direct-current power, a power converter (5) into which the direct-current power is input via the switch between two terminals on an input side and which converts the direct-current power into alternating-current power through a switching action and drives an alternating current rotating machine (13) connected on an output side, and a voltage detector (15) for detecting the voltage between the two terminals. In addition, a power controller (14) is provided that controls the power converter such that when the detected voltage of the voltage detector exceeds a predetermined open-circuit voltage, the switch is opened and the regenerative brake force is reduced by the alternating current rotating machine under a predetermined reduction pattern having a ramp reduction time longer than 0.